Hydraulic pressure multiplying system



May 25, 1948. H. E. PAGE HYDRAULIC PRESSURE MULTIPLYING SYSTEM Filed Jan. 31, 1944 2 Sheets-Sheet 1 May 25, 1948. H. E. PAGE 5 HYDRAULIC PRESSURE MULTIPLYING SYSTEM Filed Jan. 31', 1944 2 Sheets-Sheet 2 v Patented May 25, 1948 HYDRAULIiJ PRESSURE MULTIPLYING SYSTEM Herbert E. Page, Pasadena, Calif. Application January 31, 1944. Serial No. 520,411 7 Claims. (Cl. 60-545) 1 This invention has to do with hydraulic pressure multiplying apparatus and relates more particularly to main hydraulic fluid supply units or cylinders for use in hydraulic systems.

For instance, in hydraulic braking systems it has long been an aim oi those working in the art to accomplish, with a given movement of the braking pedal, a relatively rapid movement of the braking shoe into initial contact with the drum and then to automatically convert the fluid pressure into braking applying force at a relatively higher ratio. In my copending application Serial No. 516,762, filed January 3, 1944, I show a new type of braking unit for installation in the brake drums, which accomplishes this end regardless or the type of master cylinder used.

My present invention has for one of its aims the provision of a master cylinder or main hy draulic fluid supply unit which may be substituted for conventional master cylinders and thus convert 'a conventional braking system into one in which the pressure application is made in at least two stages and wherein the pressure application is automatically converted from a low pressure high volume initial stage (to initially move the brake shoes into contact with the drums) to a high pressure low volume stage to accomplish the application of braking pressure at a higher ratio.

I have also found that my master cylinder, when used in combination with braking elements mounted in the wheel drums of the character shown in my said copending application, produces a braking system affording tremendous advantages, and it is therefore one of my objects to provide a master cylinder utilizing such multistage application of pressure in combination with multi-stage pressure applying units mounted in the brake drums.

Still further objects and advantages are inherent in my invention and how-those as well as the objects hereinabove pointed out are achieved will be best understood from the following description. While in the following specification I shall describe in detail one of the physical forms which my invention may take, I Wish it understood that the invention, in its broader aspects, is not to be limited to such described details. In the accompanying drawings, which form a part hereof:

Fig. 1 is a longitudinal sectional view of my improved master cylinder; and

Fig. 2 is a fragmentary medial section of a wheel braking unit.

Referring to the drawings, I show at 5 a body providing a fluid reservoir R and a cylinder 6 separated from the reservoir by a reduced diameter portion 8a.

A piston 8 reciprocatesin cylinder 6 and has a reduced diameter portion 8a reciprocating through the reduced cylinder portion 6a. The

piston has a longitudinal bore 9 in which a piston Ill reciprocates, piston Ill passing through an opening I I in the body and being urged outwardly by a spring 1 I4 hearing at one end against the body and at its other end against an annular flange Illa on the piston. A rod "carried by the outer end of the piston I0 is adapted to operatively connect the piston to a conventional brake pedal, not shown.

Piston 8 provides, with the inner end portion of the cylinder 6, a pressure chamber 15 and the bore 9 providesa pressure chamber IS.

The outer end of. cylinder 6 is closed by a cap is which has an outlet port I 9 adapted to be connected to the braking units in the wheel drums, as by a tube 20. A wheel braking unit W is shown in Fig. 2. A spring 22, seating at one end against the piston 8 and at its other end in a recess in cap l8, normally urges the piston rearwardly in the cylinder. A fluid chamber 24 is provided by the outer end oi the piston 8, cylinder 6 and end cap l8.

The body is provided with fluid passageways 25, 26, 21, 28, the purpose of which will appear hereinafter. Passage 25 is controlled by a ball check valve 29 seating towards the reservoir and urged against its seat by a spring 30 which bears at its other end against a threaded adjusting plug 3|. Passage 2! is controlled by a ball check valve 32 seating towards the reservoir R and is urged against its seat by a spring 33 which bears at its other end against a threaded adjusting plug 34;

Piston 8 has port 35 providing communication from chamber i5 to reservoir via a port 50, a poppet 36, having seal ring 36a, controlling said communication, being normally urged against its seat (towards chamber i5) by a spring 31 bearing at its outer end against adjusting plug 38. The rearward end 0i. poppet 36 is exposed to pressure in chamber l8 through a port 34. A

port 40 in piston 8 provides communication between chambers l6 and IS in the opposite direction, bein controlled by a poppet 4| seating towards chamber l6 and normally urged seated by a spring 42 which bears at its other end against a threaded adjusting plug 43 and is yieldable to predetermined pressure in chamber It.

A port 45 in piston 8 provides communication between reservoir R and chamber I 8 via a ort wheel cylinder per se is more particularly de-- scribed and claimed in my above-mentioned coending application.

In Fig. 2 I show a wheel braking unit W comprising a body 60 secured to a backing plate SI of a brake drum 63. The backing plate may b ecured to the axle housing in conventional manner, while the drum 63 is secured to the wheel to bebraked.

Brake shoes 65 are mounted in the drum and swlngably secured to the backing plate. The free ends of the shoes are pivotally connected to the connecting rod I36 of the hydraulic unit by links '87 and pins 68. The opposite ends or the shoes are pivotally secured to the backing plate by a pivot pin, not shown, and their free ends are normally urged together by retractile springs 88, which springs are secured at one end to the respective shoes and at their other ends to the body til. The body has attaching flanges 80a by which they are secured to the backing plate.

Body 60 provides a hydraulic fluid reservoir R. and cylinders 18, I I. A piston 15 has asmaller diameter inner end portion 15a reciprocally mountedin cylinder ill and a larger diameter outer end portion 15b reciprocally mounted in cylinder H. The inner end of piston 15a forms with the inner end of cylinder a pressure chamber 11 which communicates with fluid chamber 24 of the master cylinder through a port I8 and port 86, which latter port is in communication with the fluid chamber 24 by a tube 20.

The relatively large diameter portion 15b forms with the inner end of cylinder II a pressure chamber 82 which communicates with chamber I'I through a longitudinal bore 83, radial slots 86, in piston 15a, and an annular chamber 85 provided by the reduced diameter portion 88 of piston 75a. 7

A ball check valve 81 seats towards chamber il in bore 83, being yieldably urged against its seat by a spring 88, which spring bears at its other end against the inner end of rod '65, said rod being threaded into a recess in the end of the piston and being provided with a seal ring 89.

The piston is also provided with seal rings 90.- Spring 88 is ofa strength sufllcient to maintain ball 81 on its seat against pressure in chamber 11 4 chamber 24 of the master cylinder the springs 69 and a spring 85, which bears at one end against a projection 85 on the backing plate and at its other end against the outer end of rod 68, will move the shoes away from the drum and will force the piston i5 inwardly. During this movement, fluid in chamber 82 is returned to the reservoir through a port I00 provided by sleeve IOIla and body port IIlI. During the braking pressure, port IE0 is maintained closed by a poppet valve I02 carrying a seal ring I03 and reciprocally disposed in a pressure chamber I04, which chamber I04 is in communication with the fluid until the piston is moved outwardly to initially contact the lining a of the shoes 85 with the drum, at which time the spring will yield to pressure in chamber 11 to pass fluid from that chambar into chamber 82 to apply the braking pressure at a different volume-pressure ratio.

During the initial movement or the piston to initially move the shoe linings into braking contact with the drum, during which movement a vacuum will be createdin chamber 82, make-up fluid is drawn into that chamber from the reservoir through a port 92 which is controlled by a spring-pressed ball check valve 93 seating towards the reservoir.

Upon release of the fluid pressure in fluid chamber 24 of the master cylinder so that the poppet I 02 is maintained seated by fluid pressure. Thus, when the fluid pressure in chamber 24 is relieved, poppet I82 maybe readily unseated by pressure in chamber 82. Any excess fluid in reservoir R may be returned to chamber 24 when piston 15 is retracted, by passing from the reservoir through a port I88, past springpressed check valve I81, which valve seats towards the reservoir, and thence outwardly through port 80;

Operation of the system is as follows: Initial pressure on the conventional braking pedal moves piston l0 inwardly oi bore 9, and spring 42 being sufliciently strong to maintain p pp t 4| seated when there is no substantial resistance to movement of piston 8 into the fluid chamber 24, said piston 8 will move into fluid chamber 24 relatively rapidly and thus force fluid through tube 20 into chamber i1 01' the wheel braking unit, which in turn relatively rapidly moves piston I! outwardly to initially establish contact of the shoe linings with the. drum, During this initial movement of piston 8, make-up fluid is drawn into chamber is through port 21 and pest p ppet 32. After initial contact of the shoes with the drums is thus established, the spring-pressed poppet AI will yield to pressure in chamber I8 and fluid under pressure will be passed into chamber i5. This pressure also acts against the bottom of poppet 35 and, in conjunction with the spring 37, maintains poppet 88 seated against pressure in chamber I5. Thus the braking pressure may be applied not only through a more I6 and spring 22 returns piston 8 to its starting position shown in the drawings. During this operation the fluid in chamber It is returned to thereservoir through port 60, past poppet 36.

Any depletion of the fluid within the fluid chamber 24 and the wheel unit W may bemade up by fluid being drawn from the reservoir R. through port 25.

So that there may not occur any pressure lock in chamber I6 preventing return of piston 8 to starting position, a radial port 65 is provided in piston portion 8a providing communication between chamber I8 immediately in front of piston I0, when the latter is retracted, and reservoir R;

I claim: 7 I 1. In a hydraulic braking system, a master fluid pressure supply member comprising: a body providing a fluid reservoir and a cylinder, a piston mounted for reciprocation in the cylinder and having a longitudinal bore providing a primary pressure chamber, the rear pressure-receiving face of the piston forming with the cylinder a main pressure chamber and the opposite face of the piston forming with the cylinder a fluid chamber, spring means yieldably bearing against the piston to urge it rearwardly in the cylinder, a pressure generating piston mounted for reciprocation in the primary chamber to generate fluid pressure therein, a port in the piston providing communication from the primary to the main chamber, valve means controlling said port, said valve being yieldable to predetermined pressure in the primary chamber to pass fluid to the main chamber, a fluid passageway in the body providing communication irom the reservoir to the main chamber, valve means controlling said fluid passageway, said valve means being yield: able to vacuum in the main chamber, and means responsive to pressure on the piston by the spring means when the primary chamber is not under pressure to pass fluid from the main chamber to the reservoir.

2. In a hydraulic braking system, a master fluid pressure supply member comprising: a bodyproviding a fluid reservoir and a cylinder, a piston mounted for reciprocation in the cylinder and having a longitudinal bore providing a primary pressure chamber, the rear pressure-receiving face of the piston forming with the cylinder a main pressure chamber and the opposite face of the piston forming with the cylinder a fluid chamber, spring means yleldably bearing against the piston to urge it rearwardly in the cylinder, a pressure generating piston mounted for reciprocation in the primary chamber to generate fluid pressure therein, a port in the piston providing communication from the primary to the main chamber, valve means controlling said port, said valve being yieldable to predetermined pressure in the primary chamber to pass fluid to the main chamber, a fluid passageway in the body providing communication from the reservoir to the main chamber, valve means controlling said fluid passageway, said valve means being yieldable to vacuum in the main chamber, and means responsive to pressure on the piston by the spring means when the primary chamber is not under pressure to pass fluid from the main chamber, said means comprising a fluid-passing port in the piston providing communication from the main chamber to the reservoir, a poppet valve in said port seating towards the main chamber, said poppet being yieldable to open the fluid-passing port in response to pressure exerted on the piston by said spring means when pressure is relieved in the primary chamber, and means for communicating fluid pressure generated in the primary chamber to the rear face of the poppet.

3. In a hydraulic braking system, a master fluid pressure supply member comprising: a body providing a fluid reservoir and a cylinder, a piston mounted for reciprocation in the cylinder and having a longitudinal bore providing a primary pressure chamber, the rear pressure-receiving face of the piston forming with the cylinder a main pressure chamber and the opposite face of the piston forming with the cylinder a fluid chamber, spring means yieldably bearing against the piston to urge it rearwardly in the cylinder, a pressure-generating piston mounted for reciprocation in the primary chamber to generate fluid pressure therein, a port in the piston providing communication from the primary to the main chamber, valve means controlling said port,

sure in the primary chamber to pass fluid to the main chamber, a fluid passageway in the body providing communication from the reservoir to the main chamber, valve means controlling said fluid passageway, said valve means being yieldable to vacuum in the main chamber, means responsive to pressure on the piston by the spring means when the primary chamber is not under pressure to pass fluid from the main chamber,

said means comprising a fluid-passing port in the piston providing communication from the main chamber to the reservoir, a poppet'valve in said port seating towards the main chamber, said poppet being yieldable to open the fluid-passing port in response to pressure exerted on the piston 4 by said spring means when pressure is relieved in the primary chamber, means for communicating fluid pressure generated in the primary chamber to the rear face of the poppet, a passageway in the body providing communication from the reservoir to the fluid chamber, and a valve controlling said passageway, said lastnamed valve being yieldable to open the passageway lnresponse to vacuum in the fluid chamber.

4. Ina hydraulic braking system, a master fluid pressure supply member comprising: a body providing a fluid reservoir and a cylinder, a piston mounted for reciprocation in the cylinder and having a. longitudinal bore providing a primary pressure chamber, the rear pressure-receiving face of the piston forming with the cylinder a main pressure chamber and the opposite face of the piston forming with the cylinder a fluid chamber, spring means yieldably bearing against the piston to urge it rearwardly in the cylinder, a pressure-generating piston mounted for reciprocation in the primary chamber to generate fluid pressure therein, a, port in the piston providing vacuum in the main chamber, means responsive to pressure on the piston by the spring means when the primary chamber is not under pressure to pass fluid from the main chamber, a passageway in the piston providing fluid communication from the reservoir to the primary chamber, and a check valve controlling said last-named passageway, said last-named valve being yieldable to open said passageway in response to vacuum in the primary chamber.

5. In a hydraulic braking system, a master fluid pressure supply member comprising: a body providing a fluid reservoir and a, cylinder, a. piston mounted for reciprocation in the cylinder and having a longitudinal bore providing a primary pressure chamber, the rear pressure-receiving race of the piston forming'with the cylinder a main pressure chamber and the opposite face 0f the piston forming with the cylinder a fluid chamber, spring means yieldably bearing against the piston to urge it rearwardly in the cylinder, a pressure-generating piston mounted for reciprocation in the primary chamber to generate fluid pressure therein, a port in the piston providing communication from the primary to the main chamber, valve means controlling said port, said valve being yieldable to predetermined pressure in the primary chamber to pass fluid to the main chamber, a fluid passageway in the body providing communication from the reservoir to the main chamber, valve means controlling said fluid passageway, said valve means being yieldable to vacuum in the main chamber, means responsive to pressure on the piston by the spring means when the primary chamber is not under pressure to pass fluid from the main chamber, and spring means yieldably urgingthe pressure-generating piston outwardly of the primary chamber.

6. In a hydraulic braking system, a master fluid pressure supply member comprising a. body having a fluid reservoir and a fluid chamber, a piston having a head portion mounted for reciprocation in the fluid chamber and having a rearward portion extending into the reservoir, a longitudinal bore in the piston opening through the rearward end thereof and providing a primary pressure chamber, a port connecting the primary pressure chamber to the reservoir, a, check valve in said port seating towards the reservoir, 2, spring yieidably urging said check valve seated, said spring being yieldable in response to vacuum in the primary pressure chamber, means providing a main pressure chamber annularly of the rearward portion oi the piston and behind the head portion of said piston, a port providing communication between the primary pressure chamber and the main pressure chamber, a check valve in the last-named port seating towards the primary chamber, spring means yieldably urging the last-named valve seated, said lastnamed spring means being yieldable in response to predetermined pressure in the primary pressure chamber, a passageway in the piston providing communication between the reservoir and the main pressure chamber, a check valve in said passageway seating towards the reservoir, a spring urging the last-named check valve seated and being yieldable in response to vacuum in the main pressure chamber, a pressure release port in the piston providing communication between the main chamber and the reservoir, a. check valve in the pressure release port seating towards the main pressure chamber, said last-named check valve being seated in response to fluid pressure in the primary pressure chamber, spring means interposed between the front face of the piston head and the outer end of the fluid chamber and operable to move the piston inwardly of the fluid chamber when pressure is released from the primary pressure chamber, a fluid-passing port in the body communicating with the fluid chamber at a point in front or the piston head, and a passageway in the body providing communication between the reservoir and the fluid chamber at a, point spaced outwardly from the front oi the cylinder head.

7. In a hydraulic braking system. a master fluid pressure supply member comprising a body having a fluid reservoir and a fluid chamber, a piston having a head portion mounted for reciprocation in the fluid chamber and having a rearward portion extending into the reservoir, a longitudinal bore in the piston opening through the rearward end thereof and providing a primary pressure chamber, a port connecting the primary pressure chamber to the reservoir, 9. check valve in said port seating towards the reservoir, a spring yieldably urging said check valve seated, said spring being yieldable in response to vacuum in the primary pressure chamber, means providing a I main pressure chamber annularly' oi the rearward portion of the piston and behind the head portion of said piston, a port providing communication between the primary pressure chamber and the main pressure chamber, a, check valve in the last-named port seating towards the primary chamber, spring means yieldably urging the last-named valve seated, said last-named spring means being yieldable in response to pr determined pressure in the' primary pressure chamber, a passageway in the piston providing communication between the reservoir and the main pressure chamber, a check valve in said passageway seating towards the reservoir, a spring urging the last-named check valve seated and being yieldable in response to vacuum in the main pressure chamber, a pressure release port in the piston providing communication between the main chamber and the reservoir, acheck valve in'the pressure release port seating towards the main pressure chamber, said last-named check valve being seated in response'to fluid pressure in the primary pressure chamber, spring means interposed between the front face of the piston head and the outer end of the fiuid chamber and operable to move the piston inwardly of the fluid chamber when pressure is released from the primary pressure chamber, a fluid-passing port in the body communicating with the fluid REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,958,722 Sinclair May 15,1934 2,170,851 Carroll Aug. 29, 1939 2,220,829 Rouch Nov. 5. 1940 2,277,336 Loweke Mar, 24, 1942 2,343,900v Groves Mar. 14, 1944 

